Captain McBain wrote:
How far does Geordi's authority go when it comes to Engineering? Data outranks him, but Geordi, on account of being Chief Engineer, is able to tell Data what to do. So, if Picard or Riker were in Engineering, or a visiting commander, could Geordi tell them what to do?
As Chief Engineer, Geordi is in charge of everyone in the ship's Engineering Department. Data is Second Officer so he is Geordi's superior officer in position and rank, as are Picard and Riker. Geordi would have to follow their orders. A visiting commander would have no authority when on the Enterprise.